Questions regarding temperature gradient in thermocouples.

[f_nosferatu]

Hi folks!

I was wondering if anyone can help me with a problem I'm having with the concept of thermocouples.

If I understand correctly, there should necessarily exist a temperature GRADIENT in one of the conductive couples in order for the emf to be generated. So how can you make sure that such a gradient exists in your application? I mean, imagine a TC used in a boiler with constant T. Won't the heat eventually propagate through the whole TC and eliminate the temperature gradient?

Some help will be much appreciated.

Thanks!

 

[anorlunda]

You are correct that there must be a temperature gradient.

The usual way we achieve that is to leave one side of the thermocouple exposed to ambient temperature air. In the boiler case, we could attach a termocouple to the outside wall, but not immerse it in the boiling water.

Other devices, such as the RTD can be used in places where thermocouples can not.